They should be color fast and the adhesive water soluble. Simply soaking them in warm water should allow them to pealed off the paper. If they don't slide off, you may have to find another solvent to use, available through stamp supply stores. Avoid soaking stamps on red paper or with water soluble inks.
Yes, they are collectible. The US Postal service has jobbed out the printing of stamps and one of the requirements is that the glue on self-stick stamps be water soluble. That allows collectors to soak the stamps off envelopes so they can be put in albums.
Stamps did not exist in that year. They were introduced in 1840 in Great Britain.
The US issued the first postage stamps in 1847.
The most common process is by soaking. Soak the stamps in cold water. After about fifteen minutes, most stamps will slide off of the paper. You would then dry them on blotting paper or towels. Weight is useful in keeping them flat. Also, be cautious of bright colored envelope bits. Red is particularly nasty, soak them separately from the others unless you want pink stamps!
It varies from year to year for the cost of postage stamps. Right now in 2010, it cost around 44 cents for stamps..
Hundreds of stamps are issued each year around the world. Each country will issue different stamps throughout the year.
You can purchase 7 cents stamps at the post office if they have them in stock. If you are looking for 2007 stamps, they can be purchased through dealers. The USPS sometimes has year sets available as well.
Spain
Without knowing what stamps you are refering to, it is impossible to offer a value. Stamps are issued from virtually every country in the world, as well each country issues many different stamps each year.
2011
Stamps typicall see an increase in value after the 1st year on the market. This does vary depending on the stamp.
Britain started using the metric system for currency in 1971, Stamps changed in the same year.